期刊
MOLECULAR PLANT-MICROBE INTERACTIONS
卷 27, 期 4, 页码 388-399出版社
AMER PHYTOPATHOLOGICAL SOC
DOI: 10.1094/MPMI-09-13-0284-R
关键词
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资金
- FEDER
- Fundacao para a Ciencia e a Tecnologia, Portugal [PTDC/BIA-MIC/113733/2009, PEst-OE/EQB/LA0023/2011]
- Fundação para a Ciência e a Tecnologia [PTDC/BIA-MIC/113733/2009, PEst-OE/EQB/LA0023/2013] Funding Source: FCT
The nitrogen-fixing bacterium Sinorhizobium meliloti must adapt to diverse conditions encountered during its symbiosis with leguminous plants. We characterized a new symbiotically relevant gene, emrR (SMc03169), whose product belongs to the TetR family of repressors and is divergently transcribed from emrAB genes encoding a putative major facilitator superfamily type efflux pump. An emrR deletion mutant produced more succinoglycan, displayed increased cell-wall permeability, and exhibited higher tolerance to heat shock. It also showed lower tolerance to acidic conditions, a reduced production of siderophores, and lower motility and biofilm formation. The simultaneous deletion of emrA and emrR genes restored the mentioned traits to the wild-type phenotype, except for survival under heat shock, which was lower than that displayed by the wild-type strain. Furthermore, the Delta emrR mutant as well as the double Delta emrAR mutant was impaired in symbiosis with Medicago sativa; it formed fewer nodules and competed poorly with the wild-type strain for nodule colonization. Expression profiling of the Delta emrR mutant showed decreased expression of genes involved in Nod-factor and rhizobactin biosynthesis and in stress responses. Expression of genes directing the biosynthesis of succinoglycan and other polysaccharides were increased. EmrR may therefore be involved in a regulatory network targeting membrane and cell wall modifications in preparation for colonization of root hairs during symbiosis.
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